<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      class Person {
        constructor(name, age) {
          this.name = name;
          this.age = age;
        }
        say() {
          console.log(this.name, "hello"); // cxm hello
        }
      }
      // 子类
      // extends 原型继承
      class Student extends Person {
        constructor(name, age, grade) {
          super(name, age); // 语法糖，直接改变this指向 // == Person.call(this, name, age)
          this.grade = grade;
        }
      }
      var obj = new Student();
      console.log(obj);
    </script>
  </body>
</html>
